EQuAL Student Seminar: Samuel Brantly

Magnon Optics in a vdW Antiferromagnet

Magnon spintronics promises high-speed, low-power transport inherently free from Ohmic losses due to Joule heating via the decoupling of spin excitations from their typical charge carriers. Yet, common magnonic platforms such as yttrium iron garnet (YIG) often suffer from bottlenecking losses in transduction and have been broadly difficult to integrate into nanoscale devices. An emerging class of van der Waals (vdW) magnetic materials offers an auspicious alternative that circumvents both limitations, as these materials have been shown to host exceptionally strong light-matter interactions and benefit from natural heterostructure integrability. In this talk, we extend the basic principles of guiding magnonic excitations to the class of vdW magnetic materials for the first time. By utilizing an ultrafast widefield imaging technique, we are able to reconstruct full motion pictures of magnon propagation in the vdW antiferromagnet CrSBr. We further tune the magnon dispersion via thickness engineering, which, in combination with our widefield tracking, has allowed us to establish a magnon Snell’s law for this system. Inspired by optical analogues and guided by micromagnetic simulations, we also realize a host of different reflective and transmissive devices that have allowed for the direct observation of unconventional lenses, magnonic nanojets, and whispering-gallery modes.